1. Field of the Invention
The disclosure relates generally to projectiles and, more specifically, to an apparatus, method and system for controlling the spin and/or orienting the guidance section of a projectile.
2. Description of the Related Art
The optimization of two dimensional course correction for a projectile requires a solution that is effective, has low cost, weight and power consumption. This is true for the design of a new projectile as well as the retrofit of an existing one.
One embodiment of this invention provides trajectory control by manipulation of the projectile's yaw of repose and manipulation of its drag allowing the effective course control of spinning rounds.
The use of a Magnetically Actuated Friction (MA) brake or a Magneto-Rheological (MR) fluid brake in conjunction with an external aerosurface as described in U.S. Pat. No. 7,412,930 “Frictional Roll Control Apparatus for a Spinning Projectile,” describes a low weight and low power consumption method for de-spinning and orienting the guidance section of a projectile, but fails to provide a trajectory modification method that utilizes a drag device or that utilizes a drag device in conjunction with a spin controlling method.
An electro-mechanical device can be used instead of the MA or MR brake. However, the electro-mechanical device alone would need to be large to overcome the rotational inertia of the spinning guidance section thereby requiring large amounts of power for de-spinning and orienting the guidance section of a projectile.
The use of a drag device in conjunction with the electro-mechanical device to provide the impetus to the projectile for course correction eliminates the need for a costly, weighty and power demanding system for de-spinning and orienting the guidance section of a projectile.
In addition there is a need for an invention that provides trajectory control by the “bank-to-steer” method allowing the effective course control of spinning and non-spinning rounds.
In U.S. Pat. No. 5,425,514 “Modular Aerodynamic Gyrodynamic Intelligent Controlled Projectile and Method of Operating Same,” Grosso describes as an alternative embodiment a method similar to the proposed invention however this alternative is not claimed as part of this invention. The author only specifically claims “a thrust rocket to provide a constant thrust vector in a lateral direction”. Grosso does not claim aero-surfaces as the thrust vector generator as is proposed in this invention.
In U.S. Pat. No. 4,565,340 “Guided Projectile Flight Control Fin System,” Bains describes a method for controlling the orientation the trajectory of a projectile using a set of motors to de-spin a guidance fin assembly that is then translated and pivoted to provide course correction. The proposed invention is simpler because it just rotates a guidance collar to provide the necessary force vectoring for course correction and requires only a braking mechanism, not a motor, to de-spin and reorient the guidance collar.
In U.S. Pat. No. 6,135,387 “Method for Autonomous Guidance of a Spin-Stabilized Artillery Projectile and Autonomously Guided Artillery Projectile for Realizing This Method,” Seidel, et al. describes an invention that provides a course correction by de-spinning the entire round and then guiding it with the use of actuated canards. Seidel de-spins the entire round using fins and brakes with a parachute and braking fins. The proposed invention is smaller, only de-spins the guidance collar and uses a MA or MR brake and aerodynamic forces to execute guidance. The proposed invention can be retrofitted to existing rounds whereas Seidel's invention cannot. The plurality of fins and a parachute along with various stages and an actuated guidance method make this invention wholly different from the proposed invention.
The use of non-actuated or “fixed” drag device to provide the impetus to a projectile for course correction eliminates the need for a costly, weighty and power demanding system.
The solutions described herein have the advantage of a very small, low power method of roll control for a guidance section and the absence of control actuators on the drag device reduces power consumption, cost and complexity.